Conventional office chairs use a variety of constructions for the seat assembly. Many such chairs use a sheet-like molded shell which mounts to a chair base wherein the shell supports a cushion and then a seat cover which overlies the cushion to provide the aesthetic finished appearance of the seat assembly. The cover may be formed from a variety of materials and often is formed of a fabric that can be selectively varied depending upon the pattern desired by a purchaser. In such chairs, it is necessary to secure the peripheral edge of the cover, often to the seat shell or other seat structure. In some chair constructions, separate fasteners such as staples and the like may be used to secure the peripheral edge to the inner shell.
It is an object of the invention to provide an improved seat assembly for a cushioned seat having an improved construction for securing the peripheral edge of the seat cover.
The invention relates to improved attachment structure for securing a cover in overlying covering relation to a seat cushion. In the chair of the invention, the chair comprises a seat/back assembly having a seat assembly and back assembly which are supported upon a load-bearing base adapted for support upon a floor. This base may include a tilt control mechanism wherein the seat assembly and back assembly are pivotally connected to the tilt control mechanism and rearwardly reclinable in operation. The seat assembly itself has front and rear seat portions that pivotally connect to the tilt control mechanism supported on the base. To support the seat loads, the seat assembly comprises a structurally rigid support plate which is horizontally enlarged and formed of a structurally rigid material such as metal, wherein the front and rear edge portions of the seat plate pivotally connect to the seat or to the tilt control mechanism so that the seat assembly is rearwardly tiltable in operation.
The seat assembly further comprises a horizontally enlarged, inner shell which has a bottom surface which is supported by the seat plate, and an upper surface which preferably is covered with a resiliently-compressible cushion. This cushion extends outwardly to the outer peripheral edge of the inner shell and in turn is enclosed by a seat cover, for example, formed of a fabric material, which seat cover is enlarged widthwise and in the front-to-back direction so as to hang over the sides of the cushion and wrap about the outer peripheral edge of the inner shell. As such, the peripheral cover edge is able to wrap about and extend partially underneath the bottom of the inner shell. In this edge region, the inner shell includes an edgewise-extending securement channel defined by parallel, downwardly-projecting channel walls. The inner channel wall includes spaced-apart teeth which preferably are tapered so as to facilitate compression of the cover material.
An annular outer shell is provided which mounts to the inner shell from the underside thereof and extends about the outer periphery of the inner shell. This outer shell includes an upstanding rib that extends edgewise about the periphery of the outer shell and preferably is formed of aligned ribs which are separated from each other by cross-windows. In this manner, the individual ribs are edgewise elongate so as to be generally parallel to the inner and outer channel walls of the outer shell while the individual ribs may also have some cross-wise flexure. The free ends of the ribs include additional teeth so that when the outer shell is pressed or fitted onto the inner shell from below, the peripheral cover edge follows a convoluted or treacherous path by wrapping about the outer edge of the inner shell and overlapping the underside of the inner shell, and then turning upwardly into the channel or valley as it wraps over the free ends of the ribs, and then turns downwardly out of the channel and finally extends over and terminates beyond the inner channel wall and the teeth thereof.
As the fabric passes cross-wise through this convoluted path, the cover is pinched at pinch points, wherein one pinch point preferably is located between the teeth at the upper ends of the ribs and the opposing bottom surface of the valley, and a further pinch point is located at the teeth on the inner channel wall which presses the fabric against an opposing inside surface of the outer shell. Hence, the cover material is pinched at multiple locations along the cross-wise extend of the convoluted path and thereby fixedly secured at the edge of the cover in compressed, pinched engagement between opposing surfaces of the outer shell and inner shell.
Additionally, the individual ribs are separated edge-wise by the cross-windows wherein the interior of the securement channel also includes upstanding cross-ribs which extend between the inner and outer channel walls in crosswise relation and fit into the cross-windows which thereby forces the soft cover material into the cross-windows and defines additional folds along the convoluted path of the cover material. This provides additional fixed securement of the cover when compressed between the outer shell and inner shell.
To potentially define an additional pinch point, the separation of the individual ribs from each other by the cross-windows preferably allows for outward flexing of the individual ribs when the cover material is pulled taut on the seat. Sufficient cross-wise deflection of the ribs will occur until the outer side surface of each rib contacts the interior face of the outer channel wall which thereby would serve to define an additional pinch point by pinching the cover material sidewardly or cross-wise between the rib and the outer channel wall.
The securement structure provides an improved method of securing a cover about its peripheral edge to an outer and inner shell on a seat assembly. While this structure is primarily provided for a seat assembly, a back assembly might also be configured using such securing structure.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.